Spot welding tips are conventionally made of a highly-conductive, readily-machinable material such as copper. To be most effective, the area of the metal-contacting faces of the opposed tips should be maintained flat and relatively uniform in cross section. To obtain this face uniformity, the tips are frequently given a frusto-conical shape, with the frustum of the cone becoming the flat face of the welding tip. Tip wear is frequent, due to mushrooming, pitting or accumulation of oxides from the material being welded.
Robotically-controlled welders for components and structural members of modern-day motor vehicles can require dressing of the tips every 15 or 20 production units. In critical applications where weld failure could have serious consequences, even more frequent dressing may be required. Clearly, unless the dressing operation is performed automatically, rapidly and under controlled conditions, production can be seriously hampered and tip life adversely affected. To solve this problem, stationary tool dressing machines are provided alongside such robots, and at preselected intervals, the robots move their tips to the dressing machines and simultaneously direct both opposing tips into the machines. Then, after a very brief dressing period, they return to their production stations.
Dressing tools in present-day use are typically complex and costly, frequently having several cutting edges spaced circumferentially around a tip. Because of their small size, such tools are difficult and expensive to manufacture. Further, unless they properly dress the tips, an increased incidence of weld failure can occur, and significantly reduced tip life can result.